Filter having a media retaining plate
A filtration system that includes a plurality of underdrain blocks arranged to define a plurality of laterals. Each underdrain block defines an interior and an exterior and has an orifice that provides fluid communication between the exterior and the interior. The system also includes a plurality of media retaining plates. Each plate includes a plurality of slots that extend through the plate. Each slot has an average width of less than 0.065 inches. Each plate connects to only one of the plurality of underdrain blocks such that the slots provide fluid communication between the exterior and the orifice of the underdrain block to which the plate is attached.
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This application is a continuation of patent application Ser. No. 10/186,493 filed on Jul. 1, 2002, now U.S. Pat. No. ______ which is fully incorporated herein by reference.
BACKGROUNDThe present invention relates to filters, and particularly to underdrains in gravity filters. More particularly, the present invention relates to underdrains in gravity filters having a cap or plate supporting a filter media.
Gravity filters frequently employ underdrain blocks to channel fluid away from the filter bed and to direct backwash fluids evenly into the filter bed during a backwash cycle. Underdrain blocks are assembled end to end forming rows, also known as laterals. Several laterals are placed next to one another to define the filter bottom. A filter media (e.g., granular activated carbon, anthracite, coal, magnesium oxide, ilmenite, sand including garnet, silica or quartz, etc.) placed on top of the laterals completes the filter bed and performs a majority of the filtration.
In operation, the filter bed receives a flow of fluid to be filtered and passes it through the filter media to the underdrain blocks. The size and arrangement of the filter media allows it to filter out the undesired contaminates, with finer filter media being able to filter out smaller contaminates. The flow, or filtrate, enters the underdrain blocks through openings generally provided in the tops of the underdrain blocks. The underdrain block laterals provide a convenient channel or flow path, allowing removal of the filtrate from the filter bed.
Periodically, a backwash cycle is initiated to clean the filter media. During a backwash cycle, fluid flow reverses, thus flowing into the underdrain blocks and upwardly through the filter media to loosen and remove contaminates.
It is desirable to have large openings in the filter blocks to allow free filtrate flow into the blocks. However, large openings are incapable of supporting the filter media and instead allow the media to pass into the underdrain blocks, which is undesirable. Small openings on the other hand, are capable of supporting the filter media, but are easily plugged by the filter media disposed above and upstream of the underdrain blocks. Also, small openings provide greater restriction to flow than large openings even when unclogged. Therefore, it is desirable to provide an underdrain block capable of supporting the filter media above, while simultaneously reducing the likelihood of media entering the underdrain block, and minimizing plugging of the openings. It is also desirable to provide an underdrain block having a high percentage of open surface area, thereby allowing a free fluid flow therethrough.
SUMMARYThe present invention provides a filtration system that includes a plurality of underdrain blocks arranged to define a plurality of laterals. Each underdrain block defines an interior and an exterior and has an orifice that provides fluid communication between the exterior and the interior. The system also includes a plurality of media retaining plates. Each plate includes a plurality of slots that extend through the plate. Each slot has an average width of less than 0.065 inches. Each plate connects to only one of the plurality of underdrain blocks such that the slots provide fluid communication between the exterior and the orifice of the underdrain block to which the plate is attached.
The invention further provides a filtration system that includes a block having a first wall, a second wall substantially parallel to the first wall, and a top surface substantially perpendicular to the first wall. The top surface is coupled to and is disposed between the first and second walls such that the walls and top surface at least partially define an inner chamber. The top surface includes an orifice defining a passageway between a block exterior and the inner chamber. The system also includes a plate that has a planar top surface and a planar bottom surface. A plurality of slots extend through the plate from the top surface to the bottom surface. Each slot has an average width of less than 0.065 inches and a slot outlet. The slot outlets are coplanar and the plate is coupled to the top surface and substantially covers the orifice.
In another construction, the invention provides a filtration system that includes a fluid inlet, a fluid outlet, and a plurality of underdrain blocks coupled to one another to define an underdrain lateral. Each of the underdrain blocks defines an interior and has an orifice that provides fluid communication between the fluid inlet and the interior. At least one of the blocks is in fluid communication with the fluid outlet. The system also includes a plurality of metal retaining plates. Each plate includes a planar upper surface, a planar lower surface, and a plurality of slots that extend through the plate from the upper surface to the lower surface. Each slot has a width of less than 0.065 inches. Each metal plate is coupled to one of the plurality of underdrain blocks and substantially covers the orifice. A filter media is substantially supported by the plurality of metal retaining plates and is disposed between the fluid inlet and the plurality of metal retaining plates.
In preferred embodiments, the retaining plate is manufactured from a stainless steel plate that is less than one-eight of an inch thick. The plurality of slots are preferably laser-etched through the plate and have a width between 0.002 inches and 0.025 inches. A series of longitudinal and cross members defined by the block provide support to the plate when attached to the block. In preferred embodiments, a plurality of screws attach the retaining plate to the block.
Additional features and advantages will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.
BRIEF DESCRIPTION OF THE DRAWINGSThe detailed description particularly refers to the accompanying figures in which:
As shown in
Referring to
Referring still to
The top surface 45 of the underdrain block 20 contains a number of orifices 70 sized to allow flow of filtrate into the interior of the underdrain block 20. The orifices 70, shown best in
The support grid 80 is defined by the top surface 45 of the underdrain block 20 and provides support to the media retaining plate 35. The support grid 80 also provides convenient attachment points for the media retaining plate 35. The additional support that is provided by the support grid 80 allows for the use of a thinner media retaining plate 35, if desired.
As illustrated in
The required flow area and required structural support must be balanced for the particular application to determine the exact arrangement of the long members 85 and cross members 90 of the support grid 80.
The media retaining plate 35, illustrated attached to an underdrain block 20 in
While the final thickness of the media retaining plate 35 is dependant on the specific application, it is preferred that the thickness be less than 0.25 inches, with the most common thickness being less than about 0.125 inches. In the most preferred embodiments, the media retaining plate thickness will be approximately one-sixteenth of an inch or less. It should be noted that
Referring to
The slots 95 are shaped such that the slot walls 97 remain parallel to one another throughout the thickness of the media retaining plate 35. In addition, the slot inlet flow area is substantially equal to the outlet flow area. In other words, the slot width and slot length remain constant through the thickness of the media retaining plate 35. In another embodiment (not shown), the slot walls 97 are not parallel and in fact diverge from one another as the slot 95 progresses through the media retaining plate 35. This configuration results in a slot 95 having a constant length and an increasing width through the depth of the slot 95. The total flow area of the slots 95 is determined before laser etching the slots 95 to assure a flow area at least as great as the flow area of the orifices 70. This assures that the media retaining plate 35 is not a substantial flow restriction in the filter bed 10.
Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.
Claims
1. A filtration system comprising:
- a plurality of underdrain blocks arranged to define a plurality of laterals, each underdrain block defining an interior and an exterior and having an orifice that provides fluid communication between the exterior and the interior;
- a plurality of media retaining plates, each plate including a plurality of slots extending through the plate, each slot having an average width of less than 0.065 inches, each plate connected to only one of the plurality of underdrain blocks such that the slots provide fluid communication between the exterior and the orifice of the underdrain block to which the plate is attached.
2. The filtration system of claim 1, wherein the orifice includes a plurality of apertures.
3. The filtration system of claim 1, wherein each of the media retaining plates is manufactured from a metallic material.
4. The filtration system of claim 1, wherein each of the plurality of slots defines a first wall and a second wall that is not parallel to the first wall.
5. The filtration system of claim 1, wherein each slot defines a slot top opening defining a first area and a slot bottom opening defining a second area different from the first area.
6. The filtration system of claim 1, wherein each media retaining plate defines a top surface and a bottom surface, and wherein each slot defines a first slot width at the top surface and a second slot width at the bottom surface, the second slot width different from the first slot width.
7. The filtration system of claim 6, wherein the first slot width is larger than the second slot width.
8. The filtration system of claim 1, wherein the average slot width is less than about 0.025 inches.
9. The filtration system of claim 1, further comprising a plurality of fasteners extending through each plate to attach each plate to one of the underdrain blocks.
10. A filtration system comprising:
- a block including a first wall, a second wall substantially parallel to the first wall, and a top surface substantially perpendicular to the first wall, the top surface coupled to and disposed between the first and second walls such that the walls and top surface at least partially define an inner chamber, the top surface including an orifice defining a passageway between a block exterior and the inner chamber; and
- a plate including a planar top surface and a planar bottom surface, a plurality of slots extending through the plate from the top surface to the bottom surface, each slot having an average width of less than 0.065 inches and a slot outlet, the slot outlets being coplanar, the plate being coupled to the top surface and substantially covering the orifice.
11. The filtration system of claim 10, wherein the orifice includes a plurality of apertures.
12. The filtration system of claim 10, wherein the plate is manufactured from a metallic material.
13. The filtration system of claim 10, wherein each of the plurality of slots defines a first wall and a second wall that is not parallel to the first wall.
14. The filtration system of claim 10, wherein each slot defines a slot top opening defining a first area and a slot bottom opening defining a second area different from the first area.
15. The filtration system of claim 10, wherein each slot defines a first slot width at the top surface and a second slot width at the bottom surface, the second slot width different from the first slot width.
16. The filtration system of claim 15, wherein the first slot width is larger than the second slot width.
17. The filtration system of claim 10, wherein the average slot width is less than about 0.025 inches.
18. The filtration system of claim 10, further comprising a plurality of fasteners extending through the plate to attach the plate to one of the blocks.
19. A filtration system comprising:
- a fluid inlet;
- a fluid outlet;
- a plurality of underdrain blocks coupled to one another to define an underdrain lateral, each of the underdrain blocks defining an interior and having an orifice that provides fluid communication between the fluid inlet and the interior, at least one of the blocks in fluid communication with the fluid outlet;
- a plurality of metal retaining plates each including a planar upper surface, a planar lower surface, and a plurality of slots extending through the plate from the upper surface to the lower surface, each slot having a width of less than 0.065 inches, each metal plate being coupled to one of the plurality of underdrain blocks and substantially covering the orifice; and
- a filter media substantially supported by the plurality of metal retaining plates and disposed between the fluid inlet and the plurality of metal retaining plates.
20. The filtration system of claim 19, wherein the orifice includes a plurality of apertures.
21. The filtration system of claim 19, wherein each of the plurality of slots defines a first wall and a second wall that is not parallel to the first wall.
22. The filtration system of claim 19, wherein each slot defines a first slot width at the top surface and a second slot width at the bottom surface, the second slot width different from the first slot width.
23. The filtration system of claim 22, wherein the first slot width is larger than the second slot width.
24. The filtration system of claim 19, wherein the average slot width is less than about 0.025 inches.
25. The filtration system of claim 19, further comprising a plurality of fasteners extending through each plate to attach each plate to only one of the underdrain blocks.
Type: Application
Filed: Dec 8, 2005
Publication Date: Apr 27, 2006
Patent Grant number: 7192521
Applicant: USFilter Corporation (Warrendale, PA)
Inventor: Darin St. Germain (Gilbert, IA)
Application Number: 11/297,220
International Classification: B01D 24/42 (20060101);